Advantages of the Astro-Physics Dielectric Coatings:
Reflectivity - Reflectivity is above 99% over the entire 4000 to 7000 Å photo-visual range. Thin film coatings have extremely low surface scatter compared to aluminum or enhanced aluminum coatings. Dielectric coatings (if done right) will result in less scattered light. Examination with a laser source shows approximately a 5 fold reduction in surface scatter, a tremendous improvement over aluminum mirrors.
Durability - The main advantage of a dielectric mirror coating (again, if done properly) is that the surface will be durable and will last for a lifetime. It will never tarnish and will be resistant to sleeks when cleaned. This means that for critical planetary viewing you can clean the surface and not have to worry about creating microscopic sleeks which lead to scattered light and lower contrast.
For critical planetary viewing it is important to have the eyepiece and diagonal surfaces as clean as possible. You will find that even after one observing session the diagonal surface will accumulate crud. The inherently high contrast and cleanability of the Maxbright insures that it is never a limiting factor when viewing subtle planetary detail. For cleaning instructions, see the link below and be sure to check out the Astro-Physics Optical Cleaning System (OPTCS).
Mechanical Features
Our customers have appreciated the brass locking ring on our adapters and 2" Barlow and have urged us to develop a diagonal with this feature. The recessed brass ring is under the thumbscrew location. As you tighten the thumbscrew, the brass locking ring clamps onto your eyepiece. This provides a more secure grip for your expensive eyepieces than the head of a single screw can provide. As an added advantage, the brass will not mar the surface of your accessories.
The diagonal is accurately square to the optical
axis due to the CNC machined parts and special
mounting method of the mirror. The baffles and
flat black interior allow maximum contrast.
It is threaded for 48m filters so that you can
change eyepieces with ease without changing
the filter.
Consider these dimensions to be sure that the barrel of your accessories will not strike the mirror. When using 2" accessories, the depth from the top of the diagonal to the mirror surface is 1.85". When using 1.25" accessories, the depth from the top of the diagonal to the mirror surface is 2.25"; our 1.25" adapter adds another 0.25" height. Remember that if you add filters to your eyepiece barrels, the overall length changes.
The total optical path length is 4.1", comprised of 2.75" from the center of the ocular opening to the mirror and 1.35" from the center of the objective opening to the mirror.
Cleaning
Insructions for the MaxBright Diagonal.
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